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Fixed wrong first iteration for midpoint integrator. 

Thanks to Gilles for spotting the issue.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1488969 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Luc Maisonobe 2013-06-03 12:10:36 +00:00
parent 0b2d417d52
commit e68422227f
2 changed files with 20 additions and 1 deletions
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2
src/main/java/org/apache/commons/math3/analysis/integration/MidPointIntegrator.java
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@ -120,7 +120,7 @@ public class MidPointIntegrator extends BaseAbstractUnivariateIntegrator {
final double diff = getMax() - min;
if (n == 0) {
final double midPoint = 0.5 * diff;
final double midPoint = min + 0.5 * diff;
return diff * computeObjectiveValue(midPoint);
} else {
final long np = 1L << (n - 1); // number of new points in this stage

19
src/test/java/org/apache/commons/math3/analysis/integration/MidPointIntegratorTest.java
View File

@ -35,6 +35,25 @@ import org.junit.Test;
*/
public final class MidPointIntegratorTest {
/**
* Test of integrator for the sine function.
*/
@Test
public void testLowAccuracy() {
UnivariateFunction f = new QuinticFunction();
UnivariateIntegrator integrator = new MidPointIntegrator(0.01, 1.0e-10, 2, 4);
double min = -10;
double max = -9;
double expected = -3697001.0 / 48.0;
double tolerance = FastMath.abs(expected * integrator.getRelativeAccuracy());
double result = integrator.integrate(Integer.MAX_VALUE, f, min, max);
Assert.assertTrue(integrator.getEvaluations() < Integer.MAX_VALUE / 2);
Assert.assertTrue(integrator.getIterations() < MidPointIntegrator.MIDPOINT_MAX_ITERATIONS_COUNT / 2);
Assert.assertEquals(expected, result, tolerance);
}
/**
* Test of integrator for the sine function.
*/